does great training videos on modern JavaScript stuff, mostly Angular. It's awesome to see them using CodePen - not just within the videos - but also accompanied by Embedded Pens to deliver working code examples.

Screenshot of one of their lessons:

I'm doing the same thing on my SVG course on CSS-Tricks. Not just because it doesn't hurt to show off what CodePen can do, but because it's just the right tool for the job.